1. Field of the Invention
The present invention relates to a rotary electric machine, a power distribution unit therefor, and a method for assembling rotary electric machine. More particularly, the present invention relates to a power distribution unit for a rotary electric machine with a connection ring, utilized for the connection of a stator coil of the rotary electric machine.
2. Description of Related Art
A rotating electric machine is disclosed in U.S. Pat. No. 6,034,460, which includes a stator having stator salient poles, three-phases windings wound around the stator salient poles, a rotor rotatably held inside the stator, and permanent magnets inserted into the rotor and positioned opposite to the stator salient poles. The three-phase windings are concentratively wound around each of the stator salient poles, the windings of each phase are wound around at more than one stator salient pole, and the windings of each phase have a phase difference of voltage between at least one of the windings and the other. A centralized power distribution machine, for example, a three-phase thin DC brushless motor to be used in a hybrid automobile is disclosed in U.S. Patent Application Publication No. US 2003/0173842A1. As shown in FIG. 1 of this publication, the motor 11 is disposed between an engine 12 and a transmission 13. The thin DC brushless motor 11 includes a rotor 14 connected, e.g., directly connected, to a crankshaft of the engine 12, and a ring-like stator 15 enclosing the rotor 14. The stator 15 includes a plurality of magnetic poles that have windings 16 on cores, a stator holder 18 that contains the magnetic poles, and an annular centralized distribution unit 17 that concentratedly distributes currents to the windings 16.
In a conventional power distribution unit for a rotary electric machine, a terminal of a stator coil is inserted into a through hole formed in a connecting ring and fixed thereto (for example, Japanese Laid-Open Patent Application No. 2005-86985).
Also, a conventional power distribution unit for a rotary electric machine includes ring-like lead frames for U, V, and W phases. In each of the lead frames, a connecting terminal section to be connected with a coil is formed by bending work so as to protrude inwards in the radial direction of the rotary electric machine. The lead frames for U-, V-, and W-phases overlap as seen in the direction of center axis and integrally fixed with a partial fixing unit (see, for example, Japanese Patent No. 3701639 corresponding to Japanese Laid-Open Patent Application No. 2004-96841).
However, with the construction of the power distribution unit disclosed in Japanese Laid-Open Patent Application No. 2005-86985, the part where the through hole is to be provided is pressed to form a planar part before the through hole can be fabricated. This causes the connecting part to extend in a transverse direction, i.e., in a direction of radius of the stator. As a result, it is difficult to secure a distance necessary for achieving sufficient insulation from adjacent connecting rings of other phases.
Since the surface of the connecting ring around the through hole is planar, it is somewhat difficult to insert a coil terminal into the through hole. Also, when welding of the coil terminal to the connecting ring is attempted, it is difficult to achieve an acceptable heat balance between the coil terminal to be welded and the connection ring since the volume of the molten part around the through hole is much larger than the volume of the coil terminal. This makes it difficult to perform welding.
In the construction of the power distribution unit disclosed in Japanese Laid-Open Patent Application No. 2004-96841, the lead frames for the U-, V-, and W-phases overlap as seen in the axial direction, that is, three or more connecting rings overlap as seen in the axial direction. This inevitably results in broadening of a space on an edge of the stator in the axial direction to increase the size of the rotary electric machine in the axial direction. In addition, to establish connection with a stator coil terminal, connecting parts 13 and 113 are required. Accordingly, many parts are necessary, which leads to an increase in the cost of parts and hence production cost.